Machines of that type are known, e.g. Document DE 42 09 607 describes a positive-displacement machine including a rotor which has an approximately figure-of-eight shape, i.e. the shape of a rotor of a Roots pump, and which describes orbital motion inside a stator: the axis of the rotor describes a circle, while the rotor also rotates in the opposite direction about its own axis. The stator has an outline presenting three lobes forming three chambers, each of which is provided with an intake valve and with a delivery valve.
However, such machines require eccentric drive mechanisms for providing the orbital motion, with bearings, etc. and therefore require lubricated mechanisms.